diff --git a/editor/ui/dialogs/content/EdSelectProps.js b/editor/ui/dialogs/content/EdSelectProps.js
index 24657959f4..ca58eced8e 100644
--- a/editor/ui/dialogs/content/EdSelectProps.js
+++ b/editor/ui/dialogs/content/EdSelectProps.js
@@ -8,7 +8,7 @@ var hasValue;
 var oldValue;
 var insertNew;
 var itemArray;
-var treeBoxObject;
+var theTree;
 var treeSelection;
 var selectElement;
 var currentItem = null;
@@ -94,14 +94,14 @@ optionObject.prototype.cycleCell = function cycleCell(index)
     else if (selectedOption)
     {
       selectedOption.removeAttribute("selected");
-      var column = treeBoxObject.columns["SelectSelCol"];
-      treeBoxObject.invalidateColumn(column);
+      var column = theTree.columns["SelectSelCol"];
+      theTree.invalidateColumn(column);
       selectedOption = null;
     }
     this.element.setAttribute("selected", "");
     selectedOption = this.element;
-    var column = treeBoxObject.columns["SelectSelCol"];
-    treeBoxObject.invalidateCell(index, column);
+    var column = theTree.columns["SelectSelCol"];
+    theTree.invalidateCell(index, column);
   }
   if (currentItem == this)
     // Also update the deck
@@ -178,10 +178,10 @@ optionObject.prototype.moveUp = function moveUp()
   if (itemArray[index].level < itemArray[index - 1].level + itemArray[index - 1].container)
   {
     // we need to repaint the tree's lines
-    treeBoxObject.invalidateRange(getParentIndex(index), index);
+    theTree.invalidateRange(getParentIndex(index), index);
     // a) option is just after an optgroup, so it becomes the last child
     itemArray[index].level = 2;
-    treeBoxObject.view.selectionChanged();
+    theTree.view.selectionChanged();
   }
   else
   {
@@ -206,10 +206,10 @@ optionObject.prototype.moveDown = function moveDown()
   if (index + 1 == itemArray.length || itemArray[index].level > itemArray[index + 1].level)
   {
     // we need to repaint the tree's lines
-    treeBoxObject.invalidateRange(getParentIndex(index), index);
+    theTree.invalidateRange(getParentIndex(index), index);
     // a) option is last child of an optgroup, so it moves just after
     itemArray[index].level = 1;
-    treeBoxObject.view.selectionChanged();
+    theTree.view.selectionChanged();
   }
   else
   {
@@ -292,7 +292,7 @@ optgroupObject.prototype.moveUp = function moveUp()
   var endItems = itemArray.splice(index);
   itemArray = itemArray.concat(movedItems).concat(endItems);
   // Repaint the lot
-  treeBoxObject.invalidateRange(index, j);
+  theTree.invalidateRange(index, j);
   selectTreeIndex(index, true);
 }
 
@@ -312,7 +312,7 @@ optgroupObject.prototype.moveDown = function moveDown()
   var endItems = itemArray.splice(index);
   itemArray = itemArray.concat(movedItems).concat(endItems);
   // Repaint the lot
-  treeBoxObject.invalidateRange(index, j);
+  theTree.invalidateRange(index, j);
   index += j - i;
   selectTreeIndex(index, true);
 }
@@ -321,11 +321,11 @@ optgroupObject.prototype.appendOption = function appendOption(child, parent)
 {
   var index = gDialog.nextChild(parent);
   // XXX need to repaint the lines, tree won't do this
-  var primaryCol = treeBoxObject.columns.getPrimaryColumn();
-  treeBoxObject.invalidateCell(index - 1, primaryCol);
+  var primaryCol = theTree.columns.getPrimaryColumn();
+  theTree.invalidateCell(index - 1, primaryCol);
   // insert the wrapped object as the last child
   itemArray.splice(index, 0, new optionObject(child, 2));
-  treeBoxObject.rowCountChanged(index, 1);
+  theTree.rowCountChanged(index, 1);
   selectTreeIndex(index, false);
 };
 
@@ -432,10 +432,10 @@ function Startup()
     {
       var index = itemArray.length;
       // XXX need to repaint the lines, tree won't do this
-      treeBoxObject.invalidateRange(this.lastChild(), index);
+      theTree.invalidateRange(this.lastChild(), index);
       // append the wrapped object
       itemArray.push(new optionObject(child, 1));
-      treeBoxObject.rowCountChanged(index, 1);
+      theTree.rowCountChanged(index, 1);
       selectTreeIndex(index, false);
     },
     canDestroy:       function canDestroy(prompt)
@@ -481,8 +481,8 @@ function Startup()
   UpdateSelectMultiple();
 
   // Define a custom view for the tree
-  treeBoxObject = gDialog.tree.treeBoxObject;
-  treeBoxObject.view = {
+  theTree = gDialog.tree;
+  theTree.view = {
     QueryInterface: ChromeUtils.generateQI(["nsITreeView",
                                             "nsISupportsWeakReference"]),
     // useful for debugging
@@ -628,10 +628,10 @@ function AddOptGroup()
   var optgroupElement = GetCurrentEditor().createElementWithDefaults("optgroup");
   var index = itemArray.length;
   // XXX need to repaint the lines, tree won't do this
-  treeBoxObject.invalidateRange(gDialog.lastChild(), index);
+  theTree.invalidateRange(gDialog.lastChild(), index);
   // append the wrapped object
   itemArray.push(new optgroupObject(optgroupElement));
-  treeBoxObject.rowCountChanged(index, 1);
+  theTree.rowCountChanged(index, 1);
   selectTreeIndex(index, false);
   SetTextboxFocus(gDialog.optgroupLabel);
 }
@@ -651,10 +651,10 @@ function RemoveElement()
     if (level == 1) {
       var last = gDialog.lastChild();
       if (index > last)
-        treeBoxObject.invalidateRange(last, index);
+        theTree.invalidateRange(last, index);
     }
     selectTreeIndex(index, true);
-    treeBoxObject.rowCountChanged(++index, -1);
+    theTree.rowCountChanged(++index, -1);
   }
 }
 
@@ -672,16 +672,16 @@ function onNameInput()
     gDialog.accept.disabled = disabled;
   gDialog.element.setAttribute("name", gDialog.selectName.value);
   // repaint the tree
-  var primaryCol = treeBoxObject.columns.getPrimaryColumn();
-  treeBoxObject.invalidateCell(treeSelection.currentIndex, primaryCol);
+  var primaryCol = theTree.columns.getPrimaryColumn();
+  theTree.invalidateCell(treeSelection.currentIndex, primaryCol);
 }
 
 function onLabelInput()
 {
   currentItem.element.setAttribute("label", gDialog.optgroupLabel.value);
   // repaint the tree
-  var primaryCol = treeBoxObject.columns.getPrimaryColumn();
-  treeBoxObject.invalidateCell(treeSelection.currentIndex, primaryCol);
+  var primaryCol = theTree.columns.getPrimaryColumn();
+  theTree.invalidateCell(treeSelection.currentIndex, primaryCol);
 }
 
 function onTextInput()
@@ -689,13 +689,13 @@ function onTextInput()
   currentItem.element.text = gDialog.optionText.value;
   // repaint the tree
   if (hasValue) {
-    var primaryCol = treeBoxObject.columns.getPrimaryColumn();
-    treeBoxObject.invalidateCell(treeSelection.currentIndex, primaryCol);
+    var primaryCol = theTree.columns.getPrimaryColumn();
+    theTree.invalidateCell(treeSelection.currentIndex, primaryCol);
   }
   else
   {
     gDialog.optionValue.value = gDialog.optionText.value;
-    treeBoxObject.invalidateRow(treeSelection.currentIndex);
+    theTree.invalidateRow(treeSelection.currentIndex);
   }
 }
 
@@ -705,8 +705,8 @@ function onValueInput()
   oldValue = gDialog.optionValue.value;
   currentItem.element.setAttribute("value", oldValue);
   // repaint the tree
-  var column = treeBoxObject.columns["SelectValCol"];
-  treeBoxObject.invalidateCell(treeSelection.currentIndex, column);
+  var column = theTree.columns["SelectValCol"];
+  theTree.invalidateCell(treeSelection.currentIndex, column);
 }
 
 function onHasValueClick()
@@ -724,8 +724,8 @@ function onHasValueClick()
     currentItem.element.removeAttribute("value");
   }
   // repaint the tree
-  var column = treeBoxObject.columns["SelectValCol"];
-  treeBoxObject.invalidateCell(treeSelection.currentIndex, column);
+  var column = theTree.columns["SelectValCol"];
+  theTree.invalidateCell(treeSelection.currentIndex, column);
 }
 
 function onSelectMultipleClick()
@@ -738,7 +738,7 @@ function onSelectMultipleClick()
 function selectTreeIndex(index, focus)
 {
   treeSelection.select(index);
-  treeBoxObject.ensureRowIsVisible(index);
+  theTree.ensureRowIsVisible(index);
   if (focus)
     gDialog.tree.focus();
 }
diff --git a/editor/ui/dialogs/content/EditorSaveAsCharset.js b/editor/ui/dialogs/content/EditorSaveAsCharset.js
index 948eeeea85..ae740e3af4 100644
--- a/editor/ui/dialogs/content/EditorSaveAsCharset.js
+++ b/editor/ui/dialogs/content/EditorSaveAsCharset.js
@@ -104,7 +104,7 @@ function InitDialog()
   var index = gCharsetInfo.map(info => info.value).indexOf(gCharset);
   if (index >= 0) {
     tree.view.selection.select(index);
-    tree.treeBoxObject.ensureRowIsVisible(index);
+    tree.ensureRowIsVisible(index);
   }
 }
 
diff --git a/mail/base/content/SearchDialog.js b/mail/base/content/SearchDialog.js
index 64ef786882..ebdcc7c58b 100644
--- a/mail/base/content/SearchDialog.js
+++ b/mail/base/content/SearchDialog.js
@@ -233,7 +233,6 @@ function searchOnLoad() {
   gFolderDisplay.messenger = messenger;
   gFolderDisplay.msgWindow = msgWindow;
   gFolderDisplay.tree = document.getElementById("threadTree");
-  gFolderDisplay.treeBox = gFolderDisplay.tree.boxObject;
   gFolderDisplay.view.openSearchView();
   gFolderDisplay.makeActive();
 
diff --git a/mail/base/content/folderDisplay.js b/mail/base/content/folderDisplay.js
index e0daf1be87..90e08fb1f2 100644
--- a/mail/base/content/folderDisplay.js
+++ b/mail/base/content/folderDisplay.js
@@ -111,12 +111,6 @@ function FolderDisplayWidget(aTabInfo, aMessageDisplayWidget) {
    *  responsible for setting this.
    */
   this.tree = null;
-  /**
-   * The nsITreeBoxObject on the XUL tree node, accessible from this.tree as
-   *  this.tree.boxObject and QueryInterfaced as such.  The caller is
-   *  responsible for setting this.
-   */
-  this.treeBox = null;
 
   /**
    * The nsIMsgWindow corresponding to the window that holds us.  There is only
@@ -177,19 +171,19 @@ function FolderDisplayWidget(aTabInfo, aMessageDisplayWidget) {
   });
 
   /**
-   * Create a fake tree box object for if/when this folder is in the background.
+   * Create a fake tree object for if/when this folder is in the background.
    * We need to give it a DOM object to send events to, including the onselect
    * event we care about and for which we added a handler above, and all the
    * other events we don't care about.
    */
-  this._fakeTreeBox = new FakeTreeBoxObject(domNode);
+  this._fakeTree = new FakeTree(domNode);
 
   /**
    * Create a fake tree selection for cases where we have opened a background
    * tab. We'll get rid of this as soon as we've switched to the tab for the
    * first time, and have a real tree selection.
    */
-  this._fakeTreeSelection = new JSTreeSelection(this._fakeTreeBox);
+  this._fakeTreeSelection = new JSTreeSelection(this._fakeTree);
 
   this._mostRecentSelectionCounts = [];
   this._mostRecentCurrentIndices = [];
@@ -832,7 +826,7 @@ FolderDisplayWidget.prototype = {
     this.view.close();
     this.messenger.setWindow(null, null);
     this.messenger = null;
-    this._fakeTreeBox = null;
+    this._fakeTree = null;
     this._fakeTreeSelection = null;
   },
   // @}
@@ -944,8 +938,8 @@ FolderDisplayWidget.prototype = {
     this._updateThreadDisplay();
 
     // this creates a new selection object for the view.
-    if (this.treeBox)
-      this.treeBox.view = this.view.dbView;
+    if (this.tree)
+      this.tree.view = this.view.dbView;
 
     FolderDisplayListenerManager._fireListeners("onActiveCreatedView",
                                                 [this]);
@@ -1636,9 +1630,9 @@ FolderDisplayWidget.prototype = {
       // some things only need to happen if we are transitioning from inactive
       //  to active
       if (wasInactive) {
-        if (this.treeBox) {
+        if (this.tree) {
           // We might have assigned our JS tree selection to
-          //  this.view.dbView.selection back in _hookUpFakeTreeBox. If we've
+          //  this.view.dbView.selection back in _hookUpFakeTree. If we've
           //  done so, null the selection out so that the line after this
           //  causes a real selection to be created.
           // If we haven't done so, we're fine as selection would be null here
@@ -1652,11 +1646,11 @@ FolderDisplayWidget.prototype = {
           //  out its view so that it won't try and clean up any views or their
           //  selections.  (The actual actions happen in
           //  nsTreeBodyFrame::SetView)
-          // - this.view.dbView.selection.tree = this.treeBox
-          // - this.view.dbView.setTree(this.treeBox)
-          // - this.treeBox.view = this.view.dbView (in
+          // - this.view.dbView.selection.tree = this.tree
+          // - this.view.dbView.setTree(this.tree)
+          // - this.tree.view = this.view.dbView (in
           //   nsTreeBodyObject::SetView)
-          this.treeBox.view = this.view.dbView;
+          this.tree.view = this.view.dbView;
 
           if (fakeTreeSelection) {
             fakeTreeSelection.duplicateSelection(this.view.dbView.selection);
@@ -1665,7 +1659,7 @@ FolderDisplayWidget.prototype = {
             dontReloadMessage = true;
           }
           if (this._savedFirstVisibleRow != null)
-            this.treeBox.scrollToRow(this._savedFirstVisibleRow);
+            this.tree.scrollToRow(this._savedFirstVisibleRow);
         }
       }
 
@@ -1738,14 +1732,14 @@ FolderDisplayWidget.prototype = {
       !document.getElementById("folderPaneBox").collapsed;
 
     if (this.view.dbView) {
-      if (this.treeBox)
-        this._savedFirstVisibleRow = this.treeBox.getFirstVisibleRow();
+      if (this.tree)
+        this._savedFirstVisibleRow = this.tree.getFirstVisibleRow();
 
       // save the message pane's state only when it is potentially visible
       this.messagePaneCollapsed =
         document.getElementById("messagepaneboxwrapper").collapsed;
 
-      this.hookUpFakeTreeBox(true);
+      this.hookUpFakeTree(true);
     }
 
     this.messageDisplay.makeInactive();
@@ -1762,7 +1756,7 @@ FolderDisplayWidget.prototype = {
    *          tab, for example.
    * @private
    */
-  hookUpFakeTreeBox(aNullRealTreeBoxView) {
+  hookUpFakeTree(aNullRealTreeBoxView) {
     // save off the tree selection object.  the nsTreeBodyFrame will make the
     //  view forget about it when our view is removed, so it's up to us to
     //  save it.
@@ -1772,15 +1766,15 @@ FolderDisplayWidget.prototype = {
     // if we want to, make the tree forget about the view right now so we can
     //  tell the db view about its selection object so it can try and keep it
     //  up-to-date even while hidden in the background
-    if (aNullRealTreeBoxView && this.treeBox)
-      this.treeBox.view = null;
+    if (aNullRealTreeBoxView && this.tree)
+      this.tree.view = null;
     // (and tell the db view about its selection again...)
     this.view.dbView.selection = treeSelection;
 
     // hook the dbview up to the fake tree box
-    this._fakeTreeBox.view = this.view.dbView;
-    this.view.dbView.setTree(this._fakeTreeBox);
-    treeSelection.tree = this._fakeTreeBox;
+    this._fakeTree.view = this.view.dbView;
+    this.view.dbView.setTree(this._fakeTree);
+    treeSelection.tree = this._fakeTree;
   },
 
   /**
@@ -2405,7 +2399,7 @@ FolderDisplayWidget.prototype = {
 
     // If we can get the height of the folder pane, treat the values as
     //  percentages of that.
-    if (this.treeBox) {
+    if (this.tree) {
       let topPercentPadding = Services.prefs.getIntPref(
                               "mail.threadpane.padding.top_percent");
       let bottomPercentPadding = Services.prefs.getIntPref(
@@ -2413,7 +2407,7 @@ FolderDisplayWidget.prototype = {
 
       // Assume the bottom row is half-visible and should generally be ignored.
       // (We could actually do the legwork to see if there is a partial one...)
-      let paneHeight = this.treeBox.getPageLength() - 1;
+      let paneHeight = this.tree.getPageLength() - 1;
 
       // Convert from percentages to absolute row counts.
       topPadding = Math.ceil((topPercentPadding / 100) * paneHeight);
@@ -2461,21 +2455,21 @@ FolderDisplayWidget.prototype = {
         }, 0);
     }
 
-    let treeBox = this.treeBox;
-    if (!treeBox || !treeBox.view)
+    let tree = this.tree;
+    if (!tree || !tree.view)
       return;
 
     // try and trigger a reflow...
-    treeBox.height;
+    tree.height;
 
-    let maxIndex = treeBox.view.rowCount - 1;
+    let maxIndex = tree.view.rowCount - 1;
 
-    let first = treeBox.getFirstVisibleRow();
+    let first = tree.getFirstVisibleRow();
     // Assume the bottom row is half-visible and should generally be ignored.
     // (We could actually do the legwork to see if there is a partial one...)
     const halfVisible = 1;
-    let last  = treeBox.getLastVisibleRow() - halfVisible;
-    let span = treeBox.getPageLength() - halfVisible;
+    let last  = tree.getLastVisibleRow() - halfVisible;
+    let span = tree.getPageLength() - halfVisible;
     let [topPadding, bottomPadding] = this.visibleRowPadding;
 
     let target;
@@ -2490,7 +2484,7 @@ FolderDisplayWidget.prototype = {
       return;
 
     // this sets the first visible row
-    treeBox.scrollToRow(target);
+    tree.scrollToRow(target);
   },
 
   /**
@@ -2517,13 +2511,13 @@ FolderDisplayWidget.prototype = {
         }, 0);
     }
 
-    let treeBox = this.treeBox;
-    if (!treeBox)
+    let tree = this.tree;
+    if (!tree)
       return;
-    let first = treeBox.getFirstVisibleRow();
+    let first = tree.getFirstVisibleRow();
     const halfVisible = 1;
-    let last  = treeBox.getLastVisibleRow() - halfVisible;
-    let span = treeBox.getPageLength() - halfVisible;
+    let last  = tree.getLastVisibleRow() - halfVisible;
+    let span = tree.getPageLength() - halfVisible;
     let [topPadding, bottomPadding] = this.visibleRowPadding;
 
     // bail if the range is already visible with padding constraints handled
@@ -2543,7 +2537,7 @@ FolderDisplayWidget.prototype = {
       let halfSpare = Math.floor((span - rowSpan - topPadding - bottomPadding) / 2);
       target = aMinRow - halfSpare - topPadding;
     }
-    treeBox.scrollToRow(target);
+    tree.scrollToRow(target);
   },
 
   /**
@@ -2585,11 +2579,11 @@ FolderDisplayWidget.prototype = {
  *  an event listener for onselect already attached), and pass its boxObject in
  *  whenever nsTreeSelection QIs us to nsIBoxObject.
  */
-function FakeTreeBoxObject(aDOMNode) {
+function FakeTree(aDOMNode) {
   this.domNode = aDOMNode;
   this.view = null;
 }
-FakeTreeBoxObject.prototype = {
+FakeTree.prototype = {
   view: null,
   ensureRowIsVisible() {
     // NOP
@@ -2660,7 +2654,7 @@ FakeTreeBoxObject.prototype = {
     return this.domNode.boxObject.removeProperty(propertyName);
   },
   QueryInterface: ChromeUtils.generateQI(["nsIBoxObject",
-                                          "nsITreeBoxObject"]),
+                                          "XULTreeElement"]),
 };
 /*
  * Provide attribute and function implementations that complain very loudly if
@@ -2697,7 +2691,7 @@ function FTBO_stubOutMethods(aObj, aMethodNames) {
     };
   }
 }
-FTBO_stubOutAttributes(FakeTreeBoxObject.prototype, [
+FTBO_stubOutAttributes(FakeTree.prototype, [
   "columns",
   "focused",
   "treeBody",
@@ -2706,7 +2700,7 @@ FTBO_stubOutAttributes(FakeTreeBoxObject.prototype, [
   "horizontalPosition",
   "selectionRegion",
   ]);
-FTBO_stubOutMethods(FakeTreeBoxObject.prototype, [
+FTBO_stubOutMethods(FakeTree.prototype, [
   "getFirstVisibleRow",
   "getLastVisibleRow",
   "getPageLength",
diff --git a/mail/base/content/folderPane.js b/mail/base/content/folderPane.js
index 688923a5ac..85790a236b 100644
--- a/mail/base/content/folderPane.js
+++ b/mail/base/content/folderPane.js
@@ -267,8 +267,7 @@ var gFolderTreeView = {
         aEvent.originalTarget.localName == "scrollbarbutton")
       return;
 
-    let row = gFolderTreeView._treeElement.treeBoxObject.getRowAt(aEvent.clientX,
-                                                                  aEvent.clientY);
+    let row = gFolderTreeView._treeElement.getRowAt(aEvent.clientX, aEvent.clientY);
     let folderItem = gFolderTreeView._rowMap[row];
     if (folderItem)
       folderItem.command();
@@ -278,7 +277,7 @@ var gFolderTreeView = {
   },
 
   getFolderAtCoords(aX, aY) {
-    let row = gFolderTreeView._treeElement.treeBoxObject.getRowAt(aX, aY);
+    let row = gFolderTreeView._treeElement.getRowAt(aX, aY);
     if (row in gFolderTreeView._rowMap)
       return gFolderTreeView._rowMap[row]._folder;
     return null;
@@ -574,7 +573,7 @@ var gFolderTreeView = {
     }
 
     this.selection.select(folderIndex);
-    this._treeElement.treeBoxObject.ensureRowIsVisible(folderIndex);
+    this._treeElement.ensureRowIsVisible(folderIndex);
     return true;
   },
 
diff --git a/mail/base/content/foldersummary.js b/mail/base/content/foldersummary.js
index dc4e7dd69d..b7986f7e4e 100644
--- a/mail/base/content/foldersummary.js
+++ b/mail/base/content/foldersummary.js
@@ -206,16 +206,15 @@ class MozFolderTooltip extends MozFolderSummary {
       return true;
     }
 
-    let row = {}, col = {};
-    gFolderTreeView._tree.getCellAt(event.clientX, event.clientY, row, col, {});
-    if (col.value.id == "folderNameCol") {
-      let cropped = gFolderTreeView._tree.isCellCropped(row.value, col.value);
+    let treeCellInfo = gFolderTreeView._tree.getCellAt(event.clientX, event.clientY);
+    if (treeCellInfo.col.id == "folderNameCol") {
+      let cropped = gFolderTreeView._tree.isCellCropped(treeCellInfo.row, treeCellInfo.col);
       if (this._addLocationInfo(msgFolder, cropped, tooltipnode)) {
         return true;
       }
     }
 
-    let counts = gFolderTreeView.getSummarizedCounts(row.value, col.value.id);
+    let counts = gFolderTreeView.getSummarizedCounts(treeCellInfo.row, treeCellInfo.col.id);
     return this._addSummarizeExplain(counts, tooltipnode);
   }
 
diff --git a/mail/base/content/mailCommands.js b/mail/base/content/mailCommands.js
index 71f9d7d72d..d3e5b98f47 100644
--- a/mail/base/content/mailCommands.js
+++ b/mail/base/content/mailCommands.js
@@ -306,8 +306,7 @@ function ComposeMessage(type, format, folder, messageArray) {
 function NewMessageToSelectedAddresses(type, format, identity) {
   var abSidebarPanel = document.commandDispatcher.focusedWindow;
   var abResultsTree = abSidebarPanel.document.getElementById("abResultsTree");
-  var abResultsBoxObject = abResultsTree.treeBoxObject;
-  var abView = abResultsBoxObject.view;
+  var abView = abResultsTree.view;
   abView = abView.QueryInterface(Ci.nsIAbView);
   var addresses = abView.selectedAddresses;
   var params = Cc["@mozilla.org/messengercompose/composeparams;1"].createInstance(Ci.nsIMsgComposeParams);
diff --git a/mail/base/content/mailContextMenus.js b/mail/base/content/mailContextMenus.js
index da78e9eef3..6c047114c2 100644
--- a/mail/base/content/mailContextMenus.js
+++ b/mail/base/content/mailContextMenus.js
@@ -34,7 +34,7 @@ function RestoreSelectionWithoutContentLoad(tree) {
     gRightMouseButtonSavedSelection = null;
 
     if (tree)
-      tree.treeBoxObject.invalidate();
+      tree.invalidate();
 
     UpdateMailToolbar("RestoreSelectionWithoutContentLoad");
   }
@@ -66,7 +66,7 @@ function fillMailContextMenu(event) {
   // No menu on grouped header row currently, any command would be an implied
   // multiselect.
   if (gFolderDisplay.tree) {
-    let row = gFolderDisplay.treeBox.getRowAt(event.clientX, event.clientY);
+    let row = gFolderDisplay.tree.getRowAt(event.clientX, event.clientY);
     if (gFolderDisplay.view.isGroupedByHeaderAtIndex(row)) {
       RestoreSelectionWithoutContentLoad(gFolderDisplay.tree);
       return false;
@@ -228,7 +228,7 @@ function OpenMessageByHeader(messageHeader, openInNewWindow) {
     }
 
     if (tree && tree.currentIndex != -1)
-      tree.treeBoxObject.ensureRowIsVisible(tree.currentIndex);
+      tree.ensureRowIsVisible(tree.currentIndex);
   }
 }
 
diff --git a/mail/base/content/mailTabs.js b/mail/base/content/mailTabs.js
index bb0e0f8504..a96abcce03 100644
--- a/mail/base/content/mailTabs.js
+++ b/mail/base/content/mailTabs.js
@@ -358,7 +358,7 @@ var mailTabType = {
         } else {
           // We don't want to null out the real tree box view, as that
           // corresponds to the _current_ tab, not the new one
-          aTab.folderDisplay.hookUpFakeTreeBox(false);
+          aTab.folderDisplay.hookUpFakeTree(false);
         }
       },
       persistTab(aTab) {
@@ -499,7 +499,6 @@ var mailTabType = {
     aTab.folderDisplay = new FolderDisplayWidget(aTab, aTab.messageDisplay);
     aTab.folderDisplay.msgWindow = msgWindow;
     aTab.folderDisplay.tree = document.getElementById("threadTree");
-    aTab.folderDisplay.treeBox = aTab.folderDisplay.tree.boxObject;
     aTab.folderDisplay.folderPaneVisible = aFolderPaneVisible;
 
     if (aIsFirstTab) {
diff --git a/mail/base/content/mailWidgets.xml b/mail/base/content/mailWidgets.xml
index 4f632ff169..93cd02c6bf 100644
--- a/mail/base/content/mailWidgets.xml
+++ b/mail/base/content/mailWidgets.xml
@@ -1835,10 +1835,9 @@
         <parameter name="event"/>
         <body>
           <![CDATA[
-            var box = this.tree.treeBoxObject;
-            if (event.originalTarget == box.treeBody) {
-              var index = box.getRowAt(event.clientX, event.clientY);
-              box.view.selection.select(index);
+            if (event.originalTarget == this.tree.treeBody) {
+              var index = this.tree.getRowAt(event.clientX, event.clientY);
+              this.tree.view.selection.select(index);
               return index;
             }
             return -1;
@@ -1870,17 +1869,16 @@
             self: this,
             tree: this.tree,
             parentNode: this.parentNode,
-            getLastVisibleRow(box) {
-              var f = box.getFirstVisibleRow();
-              var p = box.getPageLength();
-              var l = box.view.rowCount;
+            getLastVisibleRow(tree) {
+              var f = tree.getFirstVisibleRow();
+              var p = tree.getPageLength();
+              var l = tree.view.rowCount;
               return (l < f + p ? l : f + p) - 1;
             },
             handleEvent(event) {
               if (event.altKey)
                 return;
               var index;
-              var box = this.tree.treeBoxObject;
               if (this.parentNode.hasAttribute("open")) {
                 event.stopPropagation();
                 event.preventDefault();
@@ -1909,24 +1907,24 @@
                   break;
                 case event.DOM_VK_DOWN:
                   index++;
-                  if (index == box.view.rowCount)
+                  if (index == this.tree.view.rowCount)
                     return;
                   break;
                 case event.DOM_VK_PAGE_UP:
-                  if (index == box.getFirstVisibleRow())
-                    box.scrollByPages(-1);
-                  index = box.getFirstVisibleRow();
+                  if (index == this.tree.getFirstVisibleRow())
+                    this.tree.scrollByPages(-1);
+                  index = this.tree.getFirstVisibleRow();
                   break;
                 case event.DOM_VK_PAGE_DOWN:
-                  if (index == this.getLastVisibleRow(box))
-                    box.scrollByPages(1);
-                  index = this.getLastVisibleRow(box);
+                  if (index == this.getLastVisibleRow(this.tree))
+                    this.tree.scrollByPages(1);
+                  index = this.getLastVisibleRow(this.tree);
                   break;
                 case event.DOM_VK_HOME:
                   index = 0;
                   break;
                 case event.DOM_VK_END:
-                  index = box.view.rowCount - 1;
+                  index = this.tree.view.rowCount - 1;
                   break;
                 default:
                   if (event.charCode > 0 && !event.ctrlKey && !event.metaKey) {
@@ -1937,9 +1935,9 @@
                   }
                   return;
               }
-              box.view.selection.select(index);
+              this.tree.view.selection.select(index);
               if (this.parentNode.hasAttribute("open"))
-                box.ensureRowIsVisible(index);
+                this.tree.ensureRowIsVisible(index);
               else
                 this.self.fire();
             },
@@ -1996,14 +1994,13 @@
       <handler event="popupshowing">
         <![CDATA[
           this.parentNode.addEventListener("blur", this.onBlurMenuList);
-          var box = this.tree.treeBoxObject;
-          box.focused = true;
+          this.tree.focused = true;
           var index = this.setInitialSelection();
-          var height = box.view.rowCount * box.rowHeight;
-          height += this.boxObject.height - box.treeBody.boxObject.height;
+          var height = this.tree.view.rowCount * this.tree.rowHeight;
+          height += this.boxObject.height - this.tree.treeBody.boxObject.height;
           this.height = height;
           if (index >= 0)
-            setTimeout(function() { box.ensureRowIsVisible(index); }, 0);
+            setTimeout(function() { this.tree.ensureRowIsVisible(index); }, 0);
         ]]>
       </handler>
       <handler event="popuphiding">
diff --git a/mail/base/content/messageWindow.js b/mail/base/content/messageWindow.js
index 4d685dd825..54f8278c4d 100644
--- a/mail/base/content/messageWindow.js
+++ b/mail/base/content/messageWindow.js
@@ -91,7 +91,7 @@ StandaloneFolderDisplayWidget.prototype = {
    *  the fake tree box so it will actually do something in NoteChange.
    */
   onCreatedView() {
-    this._fakeTreeBox.view = this.view.dbView;
+    this._fakeTree.view = this.view.dbView;
     // Need to clear out this reference later.
     this._magicTreeSelection.view = this.view.dbView;
 
@@ -102,7 +102,7 @@ StandaloneFolderDisplayWidget.prototype = {
     //  showing an .eml file to go to a real message, at least in terms of
     //  having the selection object properly associated with the tree.
     if (!this.messageDisplay.isDummy) {
-      this.view.dbView.setTree(this._fakeTreeBox);
+      this.view.dbView.setTree(this._fakeTree);
       this.view.dbView.selection = this._magicTreeSelection;
       // This lets the dbView know we don't really have a tree, so it can
       // avoid operating on messages in collapsed threads.
diff --git a/mail/base/content/msgMail3PaneWindow.js b/mail/base/content/msgMail3PaneWindow.js
index a00f2810ce..a309304956 100644
--- a/mail/base/content/msgMail3PaneWindow.js
+++ b/mail/base/content/msgMail3PaneWindow.js
@@ -397,7 +397,7 @@ var MailPrefObserver = {
                                   ++currentDisplayNameVersion);
 
         // refresh the thread pane
-        threadTree.treeBoxObject.invalidate();
+        threadTree.invalidate();
       }
     }
   },
@@ -1075,15 +1075,10 @@ function ClearMessagePane() {
  *     aSingleSelect then we create a transient single-row selection.
  */
 function ChangeSelectionWithoutContentLoad(event, tree, aSingleSelect) {
-  var treeBoxObj = tree.treeBoxObject;
-  if (!treeBoxObj) {
-    event.stopPropagation();
-    return;
-  }
 
-  var treeSelection = treeBoxObj.view.selection;
+  var treeSelection = tree.view.selection;
 
-  var row = treeBoxObj.getRowAt(event.clientX, event.clientY);
+  var row = tree.getRowAt(event.clientX, event.clientY);
   // Only do something if:
   // - the row is valid
   // - it's not already selected (or we want a single selection)
@@ -1100,12 +1095,12 @@ function ChangeSelectionWithoutContentLoad(event, tree, aSingleSelect) {
       }
     }
 
-    let transientSelection = new JSTreeSelection(treeBoxObj);
+    let transientSelection = new JSTreeSelection(tree);
     transientSelection.logAdjustSelectionForReplay();
 
     gRightMouseButtonSavedSelection = {
       // Need to clear out this reference later.
-      view: treeBoxObj.view,
+      view: tree.view,
       realSelection: treeSelection,
       transientSelection,
     };
@@ -1114,14 +1109,14 @@ function ChangeSelectionWithoutContentLoad(event, tree, aSingleSelect) {
 
     // tell it to log calls to adjustSelection
     // attach it to the view
-    treeBoxObj.view.selection = transientSelection;
+    tree.view.selection = transientSelection;
     // Don't generate any selection events! (we never set this to false, because
     //  that would generate an event, and we never need one of those from this
     //  selection object.
     transientSelection.selectEventsSuppressed = true;
     transientSelection.select(row);
     transientSelection.currentIndex = saveCurrentIndex;
-    treeBoxObj.ensureRowIsVisible(row);
+    tree.ensureRowIsVisible(row);
   }
   event.stopPropagation();
 }
@@ -1154,11 +1149,8 @@ function FolderPaneOnClick(event) {
     FolderPaneContextMenuNewTab(event);
     RestoreSelectionWithoutContentLoad(folderTree);
   } else if (event.button == 0) {
-    var row = {};
-    var col = {};
-    var elt = {};
-    folderTree.treeBoxObject.getCellAt(event.clientX, event.clientY, row, col, elt);
-    if (row.value == -1) {
+    var treeCellInfo = folderTree.getCellAt(event.clientX, event.clientY);
+    if (treeCellInfo.row == -1) {
       if (event.originalTarget.localName == "treecol") {
         // clicking on the name column in the folder pane should not sort
         event.stopPropagation();
diff --git a/mail/base/content/threadPane.js b/mail/base/content/threadPane.js
index b5fc6aa706..876e67d3f7 100644
--- a/mail/base/content/threadPane.js
+++ b/mail/base/content/threadPane.js
@@ -32,28 +32,25 @@ function ThreadPaneOnClick(event) {
   if (t.localName != "treechildren")
     return;
 
-  let row = {};
-  let col = {};
-  let elt = {};
   let tree = GetThreadTree();
 
   // Figure out what cell the click was in.
-  tree.treeBoxObject.getCellAt(event.clientX, event.clientY, row, col, elt);
-  if (row.value == -1)
+  let treeCellInfo = tree.getCellAt(event.clientX, event.clientY);
+  if (treeCellInfo.row == -1)
    return;
 
   // Grouped By Sort dummy header row non cycler column doubleclick toggles the
   // thread's open/close state; tree.xml handles it. Cyclers are not currently
   // implemented in group header rows, a click/doubleclick there should
   // select/toggle thread state.
-  if (gFolderDisplay.view.isGroupedByHeaderAtIndex(row.value)) {
-    if (!col.value.cycler)
+  if (gFolderDisplay.view.isGroupedByHeaderAtIndex(treeCellInfo.row)) {
+    if (!treeCellInfo.col.cycler)
       return;
 
     if (event.detail == 1)
-      gFolderDisplay.selectViewIndex(row.value);
+      gFolderDisplay.selectViewIndex(treeCellInfo.row);
     if (event.detail == 2)
-      gFolderDisplay.view.dbView.toggleOpenState(row.value);
+      gFolderDisplay.view.dbView.toggleOpenState(treeCellInfo.row);
 
     event.stopPropagation();
     return;
@@ -61,16 +58,16 @@ function ThreadPaneOnClick(event) {
 
   // If the cell is in a cycler column or if the user doubleclicked on the
   // twisty, don't open the message in a new window.
-  if (event.detail == 2 && !col.value.cycler && elt.value != "twisty") {
+  if (event.detail == 2 && !treeCellInfo.col.cycler && treeCellInfo.childElt != "twisty") {
     ThreadPaneDoubleClick();
     // Doubleclicking should not toggle the open/close state of the thread.
     // This will happen if we don't prevent the event from bubbling to the
     // default handler in tree.xml.
     event.stopPropagation();
-  } else if (col.value.id == "junkStatusCol") {
+  } else if (treeCellInfo.col.id == "junkStatusCol") {
     MsgJunkMailInfo(true);
-  } else if (col.value.id == "threadCol" && !event.shiftKey && (event.ctrlKey || event.metaKey)) {
-    gDBView.ExpandAndSelectThreadByIndex(row.value, true);
+  } else if (treeCellInfo.col.id == "threadCol" && !event.shiftKey && (event.ctrlKey || event.metaKey)) {
+    gDBView.ExpandAndSelectThreadByIndex(treeCellInfo.row, true);
     event.stopPropagation();
   }
 }
diff --git a/mail/components/addrbook/content/abCommon.js b/mail/components/addrbook/content/abCommon.js
index e366401b04..42bb05d144 100644
--- a/mail/components/addrbook/content/abCommon.js
+++ b/mail/components/addrbook/content/abCommon.js
@@ -631,7 +631,7 @@ function DirPaneDoubleClick(event) {
     return;
 
   // Ignore double clicking on invalid rows.
-  let row = gDirTree.treeBoxObject.getRowAt(event.clientX, event.clientY);
+  let row = gDirTree.getRowAt(event.clientX, event.clientY);
   if (row == -1 || row > gDirTree.view.rowCount - 1)
     return;
 
diff --git a/mail/components/addrbook/content/abContactsPanel.js b/mail/components/addrbook/content/abContactsPanel.js
index 09d0e988bc..d92fe4c543 100644
--- a/mail/components/addrbook/content/abContactsPanel.js
+++ b/mail/components/addrbook/content/abContactsPanel.js
@@ -75,7 +75,7 @@ function contactsListOnClick(aEvent) {
   }
   // Any click on gAbResultsTree view (rows or blank space).
   if (target.localName == "treechildren") {
-    let row = gAbResultsTree.treeBoxObject.getRowAt(aEvent.clientX, aEvent.clientY);
+    let row = gAbResultsTree.getRowAt(aEvent.clientX, aEvent.clientY);
     if (row < 0 || row >= gAbResultsTree.view.rowCount) {
       // Any click on results tree whitespace.
       if ((aEvent.detail == 1 && aEvent.button == 0) || aEvent.button == 2) {
diff --git a/mail/components/extensions/test/browser/browser_ext_menus.js b/mail/components/extensions/test/browser/browser_ext_menus.js
index 14cbf8b351..1e1042bdbc 100644
--- a/mail/components/extensions/test/browser/browser_ext_menus.js
+++ b/mail/components/extensions/test/browser/browser_ext_menus.js
@@ -5,7 +5,7 @@
 let gAccount, gFolders;
 
 function treeClick(tree, row, column, event) {
-  let coords = tree.treeBoxObject.getCoordsForCellItem(row, tree.columns[column], "cell");
+  let coords = tree.getCoordsForCellItem(row, tree.columns[column], "cell");
   let treeChildren = tree.lastElementChild;
   EventUtils.synthesizeMouse(
     treeChildren,
diff --git a/mail/components/im/content/chat-messenger.js b/mail/components/im/content/chat-messenger.js
index 327feb20a0..26af33bbf8 100644
--- a/mail/components/im/content/chat-messenger.js
+++ b/mail/components/im/content/chat-messenger.js
@@ -482,7 +482,7 @@ var chatHandler = {
       if (!treeView.isContainer(index) &&
           treeView._rowMap[index].log.time == logTime) {
         logTree.view.selection.select(index);
-        logTree.treeBoxObject.ensureRowIsVisible(index);
+        logTree.ensureRowIsVisible(index);
         return true;
       }
       if (!treeView._rowMap[index].children.some(i => i.log.time == logTime))
@@ -494,7 +494,7 @@ var chatHandler = {
         ++index;
       if (treeView._rowMap[index].log.time == logTime) {
         logTree.view.selection.select(index);
-        logTree.treeBoxObject.ensureRowIsVisible(index);
+        logTree.ensureRowIsVisible(index);
       }
       return true;
     }
diff --git a/mail/components/preferences/cookies.js b/mail/components/preferences/cookies.js
index e87df27268..f7c8aa09c1 100644
--- a/mail/components/preferences/cookies.js
+++ b/mail/components/preferences/cookies.js
@@ -37,7 +37,7 @@ var gCookiesWindow = {
 
   _populateList(aInitialLoad) {
     this._loadCookies();
-    this._tree.treeBoxObject.view = this._view;
+    this._tree.view = this._view;
     if (aInitialLoad)
       this.sort("rawHost");
     if (this._view.rowCount > 0)
@@ -79,7 +79,7 @@ var gCookiesWindow = {
 
       var oldRowCount = this._view._rowCount;
       this._view._rowCount = 0;
-      this._tree.treeBoxObject.rowCountChanged(0, -oldRowCount);
+      this._tree.rowCountChanged(0, -oldRowCount);
       this._view.selection.clearSelection();
     } else if (aData == "reload") {
       // first, clear any existing entries
@@ -137,7 +137,7 @@ var gCookiesWindow = {
     }
 
     // Make sure the tree display is up to date...
-    this._tree.treeBoxObject.invalidateRow(rowIndex);
+    this._tree.invalidateRow(rowIndex);
     // ... and if the cookie is selected, update the displayed metadata too
     if (cookieItem != null && this._view.selection.currentIndex == rowIndex)
       this._updateCookieData(cookieItem);
@@ -166,7 +166,7 @@ var gCookiesWindow = {
     // if any to get the position correct.)
     var oldRowCount = this._rowCount;
     this._view._rowCount += rowCountImpact;
-    this._tree.treeBoxObject.rowCountChanged(oldRowCount - 1, rowCountImpact);
+    this._tree.rowCountChanged(oldRowCount - 1, rowCountImpact);
 
     document.getElementById("removeAllCookies").disabled = this._view._filtered;
   },
@@ -403,8 +403,8 @@ var gCookiesWindow = {
         var delta = multiplier * item.cookies.length;
         this._rowCount += delta;
         item.open = !item.open;
-        gCookiesWindow._tree.treeBoxObject.rowCountChanged(aIndex + 1, delta);
-        gCookiesWindow._tree.treeBoxObject.invalidateRow(aIndex);
+        gCookiesWindow._tree.rowCountChanged(aIndex + 1, delta);
+        gCookiesWindow._tree.invalidateRow(aIndex);
       }
     },
     cycleHeader(aColumn) {},
@@ -608,7 +608,7 @@ var gCookiesWindow = {
     //    Before SelectedIndex: 1   Before RowCount: 4
     //    After  SelectedIndex: 1   After  RowCount: 3
     var seln = this._view.selection;
-    var tbo = this._tree.treeBoxObject;
+    var tbo = this._tree;
 
     if (seln.count < 1) return;
 
@@ -730,8 +730,8 @@ var gCookiesWindow = {
     this._view._invalidateCache(0);
     this._view.selection.clearSelection();
     this._view.selection.select(0);
-    this._tree.treeBoxObject.invalidate();
-    this._tree.treeBoxObject.ensureRowIsVisible(0);
+    this._tree.invalidate();
+    this._tree.ensureRowIsVisible(0);
 
     this._lastSortAscending = ascending;
     this._lastSortProperty = aProperty;
@@ -744,12 +744,12 @@ var gCookiesWindow = {
     // Clear the Tree Display
     this._view._filtered = false;
     this._view._rowCount = 0;
-    this._tree.treeBoxObject.rowCountChanged(0, -this._view._filterSet.length);
+    this._tree.rowCountChanged(0, -this._view._filterSet.length);
     this._view._filterSet = [];
 
     // Just reload the list to make sure deletions are respected
     this._loadCookies();
-    this._tree.treeBoxObject.view = this._view;
+    this._tree.view = this._view;
 
     // Restore sort order
     var sortby = this._lastSortProperty;
@@ -840,10 +840,10 @@ var gCookiesWindow = {
     // Clear the display
     var oldCount = view._rowCount;
     view._rowCount = 0;
-    gCookiesWindow._tree.treeBoxObject.rowCountChanged(0, -oldCount);
+    gCookiesWindow._tree.rowCountChanged(0, -oldCount);
     // Set up the filtered display
     view._rowCount = view._filterSet.length;
-    gCookiesWindow._tree.treeBoxObject.rowCountChanged(0, view.rowCount);
+    gCookiesWindow._tree.rowCountChanged(0, view.rowCount);
 
     // if the view is not empty then select the first item
     if (view.rowCount > 0)
diff --git a/mail/components/preferences/permissions.js b/mail/components/preferences/permissions.js
index 71d770f15a..4fc00d58cf 100644
--- a/mail/components/preferences/permissions.js
+++ b/mail/components/preferences/permissions.js
@@ -175,13 +175,13 @@ var gPermissionManager = {
     if (this._lastPermissionSortColumn == "statusCol") {
       this._resortPermissions();
     }
-    this._tree.treeBoxObject.invalidate();
+    this._tree.invalidate();
   },
 
   _addPermission(aPermission) {
     this._addPermissionToList(aPermission);
     ++this._view._rowCount;
-    this._tree.treeBoxObject.rowCountChanged(this._view.rowCount - 1, 1);
+    this._tree.rowCountChanged(this._view.rowCount - 1, 1);
     // Re-do the sort, since we inserted this new item at the end.
     this._resortPermissions();
   },
@@ -418,8 +418,8 @@ var gPermissionManager = {
       if (this._permissions[i].principal.origin == aPrincipal.origin) {
         this._permissions.splice(i, 1);
         this._view._rowCount--;
-        this._tree.treeBoxObject.rowCountChanged(this._view.rowCount - 1, -1);
-        this._tree.treeBoxObject.invalidate();
+        this._tree.rowCountChanged(this._view.rowCount - 1, -1);
+        this._tree.invalidate();
         break;
       }
     }
diff --git a/mail/test/mozmill/folder-display/test-right-click-middle-click-messages.js b/mail/test/mozmill/folder-display/test-right-click-middle-click-messages.js
index 9c6f112c64..32cc2286a3 100644
--- a/mail/test/mozmill/folder-display/test-right-click-middle-click-messages.js
+++ b/mail/test/mozmill/folder-display/test-right-click-middle-click-messages.js
@@ -320,12 +320,12 @@ function _middle_click_on_collapsed_thread_root_helper(aBackground) {
 
   let folderTab = mc.tabmail.currentTabInfo;
 
-  let treeBox = mc.threadTree.treeBoxObject;
+  let tree = mc.threadTree;
   // Scroll to the top, then to the bottom
-  treeBox.ensureRowIsVisible(0);
-  treeBox.scrollByLines(mc.folderDisplay.view.dbView.rowCount);
+  tree.ensureRowIsVisible(0);
+  tree.scrollByLines(mc.folderDisplay.view.dbView.rowCount);
   // Note the first visible row
-  let preFirstRow = treeBox.getFirstVisibleRow();
+  let preFirstRow = tree.getFirstVisibleRow();
 
   // Since reflowing a tree (eg when switching tabs) ensures that the current
   // index is brought into view, we need to set the current index so that we
@@ -344,9 +344,9 @@ function _middle_click_on_collapsed_thread_root_helper(aBackground) {
   }
 
   // Make sure the first visible row is still the same
-  if (treeBox.getFirstVisibleRow() != preFirstRow)
+  if (tree.getFirstVisibleRow() != preFirstRow)
     throw new Error("The first visible row should have been " + preFirstRow +
-        ", but is actually " + treeBox.getFirstVisibleRow() + ".");
+        ", but is actually " + tree.getFirstVisibleRow() + ".");
 
   close_tab(tabMessage);
 }
@@ -362,13 +362,13 @@ function _middle_click_on_expanded_thread_root_helper(aBackground) {
 
   let folderTab = mc.tabmail.currentTabInfo;
 
-  let treeBox = mc.threadTree.treeBoxObject;
+  let tree = mc.threadTree;
   // Scroll to the top, then to near (but not exactly) the bottom
-  treeBox.ensureRowIsVisible(0);
-  treeBox.scrollToRow(mc.folderDisplay.view.dbView.rowCount -
-      treeBox.getPageLength() - (NUM_MESSAGES_IN_THREAD / 2));
+  tree.ensureRowIsVisible(0);
+  tree.scrollToRow(mc.folderDisplay.view.dbView.rowCount -
+      tree.getPageLength() - (NUM_MESSAGES_IN_THREAD / 2));
   // Note the first visible row
-  let preFirstRow = treeBox.getFirstVisibleRow();
+  let preFirstRow = tree.getFirstVisibleRow();
 
   // Since reflowing a tree (eg when switching tabs) ensures that the current
   // index is brought into view, we need to set the current index so that we
@@ -387,9 +387,9 @@ function _middle_click_on_expanded_thread_root_helper(aBackground) {
   }
 
   // Make sure the first visible row is still the same
-  if (treeBox.getFirstVisibleRow() != preFirstRow)
+  if (tree.getFirstVisibleRow() != preFirstRow)
     throw new Error("The first visible row should have been " + preFirstRow +
-        ", but is actually " + treeBox.getFirstVisibleRow() + ".");
+        ", but is actually " + tree.getFirstVisibleRow() + ".");
 
   close_tab(tabMessage);
 }
diff --git a/mail/test/mozmill/shared-modules/test-folder-display-helpers.js b/mail/test/mozmill/shared-modules/test-folder-display-helpers.js
index 80dfebf234..58c4d9bb01 100644
--- a/mail/test/mozmill/shared-modules/test-folder-display-helpers.js
+++ b/mail/test/mozmill/shared-modules/test-folder-display-helpers.js
@@ -961,11 +961,11 @@ function click_tree_row(aTree, aRowIndex, aController) {
 
   let selection = aTree.view.selection;
   selection.select(aRowIndex);
-  aTree.treeBoxObject.ensureRowIsVisible(aRowIndex);
+  aTree.ensureRowIsVisible(aRowIndex);
 
   // get cell coordinates
   let column = aTree.columns[0];
-  let coords = aTree.treeBoxObject.getCoordsForCellItem(aRowIndex, column, "text");
+  let coords = aTree.getCoordsForCellItem(aRowIndex, column, "text");
 
   aController.sleep(0);
   EventUtils.synthesizeMouse(aTree.body, coords.x + 4, coords.y + 4,
@@ -1098,9 +1098,8 @@ function select_shift_click_row(aViewIndex, aController, aDoNotRequireLoad) {
 function _row_click_helper(aController, aTree, aViewIndex, aButton, aExtra) {
   // Force-focus the tree
   aTree.focus();
-  let treeBox = aTree.treeBoxObject;
   // very important, gotta be able to see the row
-  treeBox.ensureRowIsVisible(aViewIndex);
+  aTree.ensureRowIsVisible(aViewIndex);
   // coordinates of the upper left of the entire tree widget (headers included)
   let tx = aTree.boxObject.x, ty = aTree.boxObject.y;
   // coordinates of the row display region of the tree (below the headers)
@@ -1118,12 +1117,12 @@ function _row_click_helper(aController, aTree, aViewIndex, aButton, aExtra) {
     if (aExtra !== "toggle")
       rowX += 32;
   }
-  let rowY = treeBox.rowHeight * (aViewIndex - treeBox.getFirstVisibleRow()) +
-    treeBox.rowHeight / 2;
-  if (treeBox.getRowAt(x + rowX, y + rowY) != aViewIndex) {
+  let rowY = aTree.rowHeight * (aViewIndex - aTree.getFirstVisibleRow()) +
+    aTree.rowHeight / 2;
+  if (aTree.getRowAt(x + rowX, y + rowY) != aViewIndex) {
     throw new Error("Thought we would find row " + aViewIndex + " at " +
                     rowX + "," + rowY + " but we found " +
-                    treeBox.getRowAt(rowX, rowY));
+                    aTree.getRowAt(rowX, rowY));
   }
   // Generate a mouse-down for all click types; the transient selection
   // logic happens on mousedown which our tests assume is happening.  (If you
@@ -1189,10 +1188,10 @@ function middle_click_on_row(aViewIndex) {
  * Assert that the given row index is currently visible in the thread pane view.
  */
 function assert_row_visible(aViewIndex) {
-  let treeBox = mc.threadTree.treeBoxObject;
+  let tree = mc.threadTree;
 
-  if (treeBox.getFirstVisibleRow() > aViewIndex ||
-      treeBox.getLastVisibleRow() < aViewIndex)
+  if (tree.getFirstVisibleRow() > aViewIndex ||
+      tree.getLastVisibleRow() < aViewIndex)
     throw new Error("Row " + aViewIndex + " should currently be visible in " +
                     "the thread pane, but isn't.");
 }
@@ -2227,12 +2226,12 @@ function assert_visible(aViewIndexOrMessage) {
     viewIndex = _normalize_view_index(aViewIndexOrMessage);
   else
     viewIndex = mc.dbView.findIndexOfMsgHdr(aViewIndexOrMessage, false);
-  let treeBox = mc.threadTree.boxObject;
-  if (viewIndex < treeBox.getFirstVisibleRow() ||
-      viewIndex > treeBox.getLastVisibleRow())
+  let tree = mc.threadTree;
+  if (viewIndex < tree.getFirstVisibleRow() ||
+      viewIndex > tree.getLastVisibleRow())
     throw new Error("View index " + viewIndex + " is not visible! (" +
-                    treeBox.getFirstVisibleRow() + "-" +
-                    treeBox.getLastVisibleRow() + " are visible)");
+                    tree.getFirstVisibleRow() + "-" +
+                    tree.getLastVisibleRow() + " are visible)");
 }
 
 /**
diff --git a/mailnews/addrbook/content/abResultsPane.js b/mailnews/addrbook/content/abResultsPane.js
index e8849ac2db..d739d6fead 100644
--- a/mailnews/addrbook/content/abResultsPane.js
+++ b/mailnews/addrbook/content/abResultsPane.js
@@ -76,7 +76,7 @@ function SetAbView(aURI)
   var actualSortColumn = gAbView.setView(directory, GetAbViewListener(),
                                          sortColumn, sortDirection);
 
-  gAbResultsTree.treeBoxObject.view =
+  gAbResultsTree.view =
     gAbView.QueryInterface(Ci.nsITreeView);
 
   UpdateSortIndicators(actualSortColumn, sortDirection);
@@ -289,8 +289,7 @@ function AbResultsPaneOnClick(event)
   }
   else if (t.localName == "treechildren") {
     // figure out what row the click was in
-    var row = gAbResultsTree.treeBoxObject.getRowAt(event.clientX,
-                                                    event.clientY);
+    var row = gAbResultsTree.getRowAt(event.clientX, event.clientY);
     if (row == -1)
       return;
 
@@ -354,7 +353,7 @@ function UpdateSortIndicators(colID, sortDirection)
 function InvalidateResultsPane()
 {
   if (gAbResultsTree)
-    gAbResultsTree.treeBoxObject.invalidate();
+    gAbResultsTree.invalidate();
 }
 
 // Controller object for Results Pane
diff --git a/mailnews/base/content/msgSelectOfflineFolders.js b/mailnews/base/content/msgSelectOfflineFolders.js
index 2db6e0ccc7..ca294baf7d 100644
--- a/mailnews/base/content/msgSelectOfflineFolders.js
+++ b/mailnews/base/content/msgSelectOfflineFolders.js
@@ -68,15 +68,12 @@ var gSelectOffline = {
     if (aEvent.button != 0)
       return;
 
-    let row = {};
-    let col = {};
-    this._treeElement.treeBoxObject
-        .getCellAt(aEvent.clientX, aEvent.clientY, row, col, {});
+    let treeCellInfo = this._treeElement.getCellAt(aEvent.clientX);
 
-    if (row.value == -1 || col.value.id != "syncCol")
+    if (treeCellInfo.row == -1 || treeCellInfo.col.id != "syncCol")
       return;
 
-    this._toggle(row.value);
+    this._toggle(treeCellInfo.row);
   },
 
   _toggle: function(aRow) {
diff --git a/mailnews/base/content/msgSynchronize.js b/mailnews/base/content/msgSynchronize.js
index 6d6d9657bf..d366ccd3ac 100644
--- a/mailnews/base/content/msgSynchronize.js
+++ b/mailnews/base/content/msgSynchronize.js
@@ -128,19 +128,15 @@ function onSynchronizeClick(event)
     if (event.button != 0)
       return;
 
-    var row = {}
-    var col = {}
-    var elt = {}
-
-    gSynchronizeTree.treeBoxObject.getCellAt(event.clientX, event.clientY, row, col, elt);
-    if (row.value == -1)
+    let treeCellInfo = gSynchronizeTree.getCellAt(event.clientX, event.clientY);
+    if (treeCellInfo.row == -1)
       return;
 
-    if (elt.value == "twisty") {
-        var folderResource = GetFolderResource(gSynchronizeTree, row.value);
+    if (treeCellInfo.childElt == "twisty") {
+        var folderResource = GetFolderResource(gSynchronizeTree, treeCellInfo.row);
         var folder = folderResource.QueryInterface(Ci.nsIMsgFolder);
 
-        if (!(gSynchronizeTree.treeBoxObject.view.isContainerOpen(row.value))) {
+        if (!(gSynchronizeTree.view.isContainerOpen(treeCellInfo.row))) {
             var serverType = folder.server.type;
             // imap is the only server type that does folder discovery
             if (serverType != "imap") return;
@@ -158,8 +154,8 @@ function onSynchronizeClick(event)
         }
     }
     else {
-      if (col.value.id == "syncCol") {
-        UpdateNode(GetFolderResource(gSynchronizeTree, row.value), row.value);
+      if (treeCellInfo.col.id == "syncCol") {
+        UpdateNode(GetFolderResource(gSynchronizeTree, treeCellInfo.row), treeCellInfo.row);
       }
     }
 }
diff --git a/mailnews/base/content/subscribe.js b/mailnews/base/content/subscribe.js
index 6a84214360..6e0ecb1d21 100644
--- a/mailnews/base/content/subscribe.js
+++ b/mailnews/base/content/subscribe.js
@@ -7,7 +7,6 @@ ChromeUtils.import("resource:///modules/iteratorUtils.jsm");
 
 var gSubscribeTree = null;
 var gSubscribeBody = null;
-var gSearchTree;
 var okCallback = null;
 var gChangeTable = {};
 var gServerURI = null;
@@ -17,7 +16,7 @@ var gNameFieldLabel = null;
 var gStatusFeedback;
 var gSubscribeDeck = null;
 var gSearchView = null;
-var gSearchTreeBoxObject = null;
+var gSearchTree = null;
 var gSubscribeBundle;
 
 function Stop()
@@ -148,7 +147,7 @@ function SubscribeOnLoad()
   gSubscribeTree = document.getElementById("subscribeTree");
   gSubscribeBody = document.getElementById("subscribeTreeBody");
   gSearchTree = document.getElementById("searchTree");
-  gSearchTreeBoxObject = document.getElementById("searchTree").treeBoxObject;
+  gSearchTree = document.getElementById("searchTree");
   gNameField = document.getElementById("namefield");
   gNameFieldLabel = document.getElementById("namefieldlabel");
 
@@ -270,25 +269,24 @@ function SearchOnClick(event)
   // we only care about button 0 (left click) events
   if (event.button != 0 || event.originalTarget.localName != "treechildren") return;
 
-  var row = {}, col = {}, childElt = {};
-  gSearchTreeBoxObject.getCellAt(event.clientX, event.clientY, row, col, childElt);
-  if (row.value == -1 || row.value > gSearchView.rowCount-1)
+  let treeCellInfo = gSearchTree.getCellAt(event.clientX, event.clientY);
+  if (treeCellInfo.row == -1 || treeCellInfo.row > gSearchView.rowCount-1)
     return;
 
-  if (col.value.id == "subscribedColumn2") {
+  if (treeCellInfo.col.id == "subscribedColumn2") {
     if (event.detail != 2) {
       // single clicked on the check box
       // (in the "subscribedColumn2" column) reverse state
       // if double click, do nothing
-      ReverseStateFromRow(row.value);
+      ReverseStateFromRow(treeCellInfo.row);
     }
   } else if (event.detail == 2) {
     // double clicked on a row, reverse state
-    ReverseStateFromRow(row.value);
+    ReverseStateFromRow(treeCellInfo.row);
   }
 
   // invalidate the row
-  InvalidateSearchTreeRow(row.value);
+  InvalidateSearchTreeRow(treeCellInfo.row);
 }
 
 function ReverseStateFromRow(aRow)
@@ -356,16 +354,15 @@ function SubscribeOnClick(event)
   if (event.button != 0 || event.originalTarget.localName != "treechildren")
    return;
 
-  var row = {}, col = {}, obj = {};
-  gSubscribeTree.treeBoxObject.getCellAt(event.clientX, event.clientY, row, col, obj);
-  if (row.value == -1 || row.value > (gSubscribeTree.view.rowCount - 1))
+  let treeCellInfo = gSubscribeTree.getCellAt(event.clientX, event.clientY);
+  if (treeCellInfo.row == -1 || treeCellInfo.row > (gSubscribeTree.view.rowCount - 1))
     return;
 
   if (event.detail == 2) {
     // only toggle subscribed state when double clicking something
     // that isn't a container
-    if (!gSubscribeTree.view.isContainer(row.value)) {
-      ReverseStateFromNode(row.value);
+    if (!gSubscribeTree.view.isContainer(treeCellInfo.row)) {
+      ReverseStateFromNode(treeCellInfo.row);
       return;
     }
   }
@@ -373,7 +370,7 @@ function SubscribeOnClick(event)
   {
     // if the user single clicks on the subscribe check box, we handle it here
     if (col.value.id == "subscribedColumn")
-      ReverseStateFromNode(row.value);
+      ReverseStateFromNode(treeCellInfo.row);
   }
 }
 
@@ -412,12 +409,12 @@ function ShowNewGroupsList()
 
 function InvalidateSearchTreeRow(row)
 {
-    gSearchTreeBoxObject.invalidateRow(row);
+    gSearchTree.invalidateRow(row);
 }
 
 function InvalidateSearchTree()
 {
-    gSearchTreeBoxObject.invalidate();
+    gSearchTree.invalidate();
 }
 
 function SwitchToNormalView()
@@ -442,7 +439,7 @@ function Search()
     if (!gSearchView && gSubscribableServer) {
     gSearchView = gSubscribableServer.QueryInterface(Ci.nsITreeView);
       gSearchView.selection = null;
-    gSearchTreeBoxObject.view = gSearchView;
+    gSearchTree.view = gSearchView;
   }
   }
   else {
diff --git a/mailnews/base/content/virtualFolderListEdit.js b/mailnews/base/content/virtualFolderListEdit.js
index 2f582ee933..58f55ee8df 100644
--- a/mailnews/base/content/virtualFolderListEdit.js
+++ b/mailnews/base/content/virtualFolderListEdit.js
@@ -73,14 +73,11 @@ var gSelectVirtual = {
     if (aEvent.button != 0)
       return;
 
-    let row = {};
-    let col = {};
-    this._treeElement.treeBoxObject
-                     .getCellAt(aEvent.clientX, aEvent.clientY, row, col, {});
-    if (row.value == -1 || col.value.id != "selectedCol")
+    let treeCellInfo = this._treeElement.getCellAt(aEvent.clientX, aEvent.clientY);
+    if (treeCellInfo.row == -1 || treeCellInfo.col.id != "selectedCol")
       return;
 
-    this._toggle(row.value);
+    this._toggle(treeCellInfo.row);
   },
 
   _toggle: function(aRow) {
diff --git a/mailnews/base/prefs/content/AccountManager.js b/mailnews/base/prefs/content/AccountManager.js
index 668380599f..a5f165424f 100644
--- a/mailnews/base/prefs/content/AccountManager.js
+++ b/mailnews/base/prefs/content/AccountManager.js
@@ -197,13 +197,13 @@ function selectServer(server, selectPageId)
   let accountTree = document.getElementById("accounttree");
   let index = accountTree.view.getIndexOfItem(pageToSelect);
   accountTree.view.selection.select(index);
-  accountTree.treeBoxObject.ensureRowIsVisible(index);
+  accountTree.ensureRowIsVisible(index);
 
   let lastItem = accountNode.lastChild.lastChild;
   if (lastItem.localName == "treeitem")
     index = accountTree.view.getIndexOfItem(lastItem);
 
-  accountTree.treeBoxObject.ensureRowIsVisible(index);
+  accountTree.ensureRowIsVisible(index);
 }
 
 function replaceWithDefaultSmtpServer(deletedSmtpServerKey)
diff --git a/mailnews/base/util/jsTreeSelection.js b/mailnews/base/util/jsTreeSelection.js
index 999ef81a51..3186d4337e 100644
--- a/mailnews/base/util/jsTreeSelection.js
+++ b/mailnews/base/util/jsTreeSelection.js
@@ -37,8 +37,8 @@ ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
  *
  * Unit test is in mailnews/base/util/test_jsTreeSelection.js
  */
-function JSTreeSelection(aTreeBoxObject) {
-  this._treeBoxObject = aTreeBoxObject;
+function JSTreeSelection(aTree) {
+  this._tree = aTree;
 
   this._currentIndex = null;
   this._shiftSelectPivot = null;
@@ -49,9 +49,9 @@ function JSTreeSelection(aTreeBoxObject) {
 }
 JSTreeSelection.prototype = {
   /**
-   * The current nsITreeBoxObject, appropriately QueryInterfaced.  May be null.
+   * The current XULTreeElement, appropriately QueryInterfaced. May be null.
    */
-  _treeBoxObject: null,
+  _tree: null,
 
   /**
    * Where the focus rectangle (that little dotted thing) shows up.  Just
@@ -83,10 +83,10 @@ JSTreeSelection.prototype = {
   _view: null,
 
   get tree() {
-    return this._treeBoxObject;
+    return this._tree;
   },
-  set tree(aTreeBoxObject) {
-    this._treeBoxObject = aTreeBoxObject;
+  set tree(aTree) {
+    this._tree = aTree;
   },
 
   set view(aView) {
@@ -138,8 +138,8 @@ JSTreeSelection.prototype = {
     this._count = 1;
     this._ranges = [[aViewIndex, aViewIndex]];
 
-    if (this._treeBoxObject)
-      this._treeBoxObject.invalidate();
+    if (this._tree)
+      this._tree.invalidate();
 
     this._fireSelectionChanged();
   },
@@ -206,8 +206,8 @@ JSTreeSelection.prototype = {
       // otherwise we need to keep going
     }
 
-    if (this._treeBoxObject)
-      this._treeBoxObject.invalidateRow(aIndex);
+    if (this._tree)
+      this._tree.invalidateRow(aIndex);
     this._fireSelectionChanged();
   },
 
@@ -242,8 +242,8 @@ JSTreeSelection.prototype = {
     if (!aAugment) {
       this._count = aRangeEnd - aRangeStart + 1;
       this._ranges = [[aRangeStart, aRangeEnd]];
-      if (this._treeBoxObject)
-        this._treeBoxObject.invalidate();
+      if (this._tree)
+        this._tree.invalidate();
       this._fireSelectionChanged();
       return;
     }
@@ -292,8 +292,8 @@ JSTreeSelection.prototype = {
       this._ranges.splice(insertionPoint, 0, [aRangeStart, aRangeEnd]);
 
     this._updateCount();
-    if (this._treeBoxObject)
-      this._treeBoxObject.invalidate();
+    if (this._tree)
+      this._tree.invalidate();
     this._fireSelectionChanged();
   },
 
@@ -348,8 +348,8 @@ JSTreeSelection.prototype = {
     this._ranges.splice.apply(this._ranges, args);
 
     this._updateCount();
-    if (this._treeBoxObject)
-      this._treeBoxObject.invalidate();
+    if (this._tree)
+      this._tree.invalidate();
     // note! nsTreeSelection doesn't fire a selection changed event, so neither
     //  do we, but it seems like we should
   },
@@ -362,8 +362,8 @@ JSTreeSelection.prototype = {
     this._shiftSelectPivot = null;
     this._count = 0;
     this._ranges = [];
-    if (this._treeBoxObject)
-      this._treeBoxObject.invalidate();
+    if (this._tree)
+      this._tree.invalidate();
     this._fireSelectionChanged();
   },
 
@@ -391,8 +391,8 @@ JSTreeSelection.prototype = {
     this._count = rowCount;
     this._ranges = [[0, rowCount - 1]];
 
-    if (this._treeBoxObject)
-      this._treeBoxObject.invalidate();
+    if (this._tree)
+      this._tree.invalidate();
     this._fireSelectionChanged();
   },
 
@@ -407,8 +407,8 @@ JSTreeSelection.prototype = {
   },
 
   invalidateSelection: function JSTreeSelection_invalidateSelection() {
-    if (this._treeBoxObject)
-      this._treeBoxObject.invalidate();
+    if (this._tree)
+      this._tree.invalidate();
   },
 
   /**
@@ -523,8 +523,8 @@ JSTreeSelection.prototype = {
         this._ranges[iTrans] = [low + aCount, high + aCount];
       }
       // invalidate and fire selection change notice
-      if (this._treeBoxObject)
-        this._treeBoxObject.invalidate();
+      if (this._tree)
+        this._tree.invalidate();
       this._fireSelectionChanged();
       return;
     }
@@ -553,8 +553,8 @@ JSTreeSelection.prototype = {
       this._ranges.splice(iTrans, 1);
     }
 
-    if (this._treeBoxObject)
-      this._treeBoxObject.invalidate();
+    if (this._tree)
+      this._tree.invalidate();
     this.selectEventsSuppressed = saveSuppress;
   },
 
@@ -582,8 +582,8 @@ JSTreeSelection.prototype = {
     if (this.selectEventsSuppressed)
       return;
     let view;
-    if (this._treeBoxObject && this._treeBoxObject.view)
-      view = this._treeBoxObject.view;
+    if (this._tree && this._tree.view)
+      view = this._tree.view;
     else
       view = this._view;
 
@@ -609,8 +609,8 @@ JSTreeSelection.prototype = {
       return;
 
     this._currentIndex = (aIndex != -1) ? aIndex : null;
-    if (this._treeBoxObject)
-      this._treeBoxObject.invalidateRow(aIndex);
+    if (this._tree)
+      this._tree.invalidateRow(aIndex);
   },
 
   currentColumn: null,
diff --git a/mailnews/extensions/newsblog/content/FeedUtils.jsm b/mailnews/extensions/newsblog/content/FeedUtils.jsm
index eca419a84e..c5c63b051d 100644
--- a/mailnews/extensions/newsblog/content/FeedUtils.jsm
+++ b/mailnews/extensions/newsblog/content/FeedUtils.jsm
@@ -868,7 +868,7 @@ var FeedUtils = {
 
     win = Services.wm.getMostRecentWindow("Mail:News-BlogSubscriptions");
     if (win) {
-      win.FeedSubscriptions.mView.treeBox.invalidate();
+      win.FeedSubscriptions.mView.tree.invalidate();
     }
   },
 
diff --git a/mailnews/extensions/newsblog/content/feed-subscriptions.js b/mailnews/extensions/newsblog/content/feed-subscriptions.js
index f70ec5a2e4..bf042c9675 100644
--- a/mailnews/extensions/newsblog/content/feed-subscriptions.js
+++ b/mailnews/extensions/newsblog/content/feed-subscriptions.js
@@ -109,7 +109,7 @@ var FeedSubscriptions = {
       }
     }
 
-    this.mView.treeBox.ensureRowIsVisible(this.mView.selection.currentIndex);
+    this.mView.tree.ensureRowIsVisible(this.mView.selection.currentIndex);
     this.clearStatusInfo();
   },
 
@@ -130,7 +130,7 @@ var FeedSubscriptions = {
 
     /* nsITreeView */
     /* eslint-disable no-multi-spaces */
-    treeBox: null,
+    tree: null,
 
     mRowCount: 0,
     get rowCount()               { return this.mRowCount; },
@@ -139,7 +139,7 @@ var FeedSubscriptions = {
     get selection()              { return this._selection; },
     set selection(val)           { return this._selection = val; },
 
-    setTree(aTreebox)            { this.treeBox = aTreebox; },
+    setTree(aTree)               { this.tree = aTree; },
     isSeparator(aRow)            { return false; },
     isSorted()                   { return false; },
     isEditable(aRow, aColumn)    { return false; },
@@ -274,7 +274,7 @@ var FeedSubscriptions = {
 
       // Now invalidate the correct tree rows.
       this.mRowCount--;
-      this.treeBox.rowCountChanged(aRow, -1);
+      this.tree.rowCountChanged(aRow, -1);
 
       // Now update the selection position, unless noSelect (selection is
       // done later or not at all).  If the item is the last child, select the
@@ -575,7 +575,7 @@ var FeedSubscriptions = {
       // Suppress the select event caused by rowCountChanged.
       this.selection.selectEventsSuppressed = true;
       // Add or remove the children from our view.
-      this.treeBox.rowCountChanged(aRow, delta);
+      this.tree.rowCountChanged(aRow, delta);
       return delta;
     },
   },
@@ -724,8 +724,8 @@ var FeedSubscriptions = {
     let found = false;
 
     let firstVisRow, curFirstVisRow, curLastVisRow;
-    if (this.mView.treeBox) {
-      firstVisRow = this.mView.treeBox.getFirstVisibleRow();
+    if (this.mView.tree) {
+      firstVisRow = this.mView.tree.getFirstVisibleRow();
     }
 
     if (parentIndex != null) {
@@ -859,13 +859,13 @@ var FeedSubscriptions = {
     }
 
     // Ensure tree position does not jump unnecessarily.
-    curFirstVisRow = this.mView.treeBox.getFirstVisibleRow();
-    curLastVisRow = this.mView.treeBox.getLastVisibleRow();
+    curFirstVisRow = this.mView.tree.getFirstVisibleRow();
+    curLastVisRow = this.mView.tree.getLastVisibleRow();
     if (firstVisRow >= 0 &&
         this.mView.rowCount - curLastVisRow > firstVisRow - curFirstVisRow) {
-      this.mView.treeBox.scrollToRow(firstVisRow);
+      this.mView.tree.scrollToRow(firstVisRow);
     } else {
-      this.mView.treeBox.ensureRowIsVisible(this.mView.rowCount - 1);
+      this.mView.tree.ensureRowIsVisible(this.mView.rowCount - 1);
     }
 
     FeedUtils.log.debug("selectFolder: curIndex:firstVisRow:" +
@@ -905,7 +905,7 @@ var FeedSubscriptions = {
         for (let i = seln.currentIndex + 1; i < this.mView.rowCount; i++) {
           if (this.mView.getItemAtIndex(i).url == aFeed.url) {
             this.mView.selection.select(i);
-            this.mView.treeBox.ensureRowIsVisible(i);
+            this.mView.tree.ensureRowIsVisible(i);
             found = true;
             break;
           }
@@ -1988,7 +1988,7 @@ var FeedSubscriptions = {
 
       let feedWindow = this.feedWindow;
       let curSelItem = this.currentSelectedItem;
-      let firstVisRow = feedWindow.mView.treeBox.getFirstVisibleRow();
+      let firstVisRow = feedWindow.mView.tree.getFirstVisibleRow();
       let indexInView = feedWindow.mView.getItemInViewIndex(parentFolder);
       let open = indexInView != null;
 
@@ -2001,7 +2001,7 @@ var FeedSubscriptions = {
           feedWindow.mFeedContainers.push(feedWindow.makeFolderObject(parentFolder, 0));
           feedWindow.mView.mRowCount++;
           feedWindow.mTree.view = feedWindow.mView;
-          feedWindow.mView.treeBox.scrollToRow(firstVisRow);
+          feedWindow.mView.tree.scrollToRow(firstVisRow);
           return;
         }
       }
@@ -2028,7 +2028,7 @@ var FeedSubscriptions = {
         feedWindow.mView.toggleOpenState(parentIndex);
       }
 
-      feedWindow.mView.treeBox.scrollToRow(firstVisRow);
+      feedWindow.mView.tree.scrollToRow(firstVisRow);
 
       if (curSelItem.container) {
         feedWindow.selectFolder(curSelItem.folder, { open: curSelItem.open });
@@ -2083,7 +2083,7 @@ var FeedSubscriptions = {
       let feedWindow = this.feedWindow;
       let curSelIndex = this.currentSelectedIndex;
       let curSelItem = this.currentSelectedItem;
-      let firstVisRow = feedWindow.mView.treeBox.getFirstVisibleRow();
+      let firstVisRow = feedWindow.mView.tree.getFirstVisibleRow();
       let indexInView = feedWindow.mView.getItemInViewIndex(aOrigFolder);
       let open = indexInView != null;
 
@@ -2109,7 +2109,7 @@ var FeedSubscriptions = {
 
       feedWindow.mView.toggle(parentIndex);
       feedWindow.mView.toggleOpenState(parentIndex);
-      feedWindow.mView.treeBox.scrollToRow(firstVisRow);
+      feedWindow.mView.tree.scrollToRow(firstVisRow);
 
       if (curSelItem.container) {
         if (curSelItem.folder == aOrigFolder) {
@@ -2139,7 +2139,7 @@ var FeedSubscriptions = {
       let feedWindow = this.feedWindow;
       let curSelIndex = this.currentSelectedIndex;
       let curSelItem = this.currentSelectedItem;
-      let firstVisRow = feedWindow.mView.treeBox.getFirstVisibleRow();
+      let firstVisRow = feedWindow.mView.tree.getFirstVisibleRow();
       let indexInView = feedWindow.mView.getItemInViewIndex(aSrcFolder);
       let destIndexInView = feedWindow.mView.getItemInViewIndex(aDestFolder);
       let open = indexInView != null || destIndexInView != null;
@@ -2169,7 +2169,7 @@ var FeedSubscriptions = {
 
         feedWindow.mView.toggle(parentIndex);
         feedWindow.mView.toggleOpenState(parentIndex);
-        feedWindow.mView.treeBox.scrollToRow(firstVisRow);
+        feedWindow.mView.tree.scrollToRow(firstVisRow);
 
         if (curSelItem.container) {
           if (curSelItem.folder == aSrcFolder || select) {
diff --git a/mailnews/extensions/newsblog/content/newsblogOverlay.js b/mailnews/extensions/newsblog/content/newsblogOverlay.js
index 2717ea6e6c..f32866db02 100755
--- a/mailnews/extensions/newsblog/content/newsblogOverlay.js
+++ b/mailnews/extensions/newsblog/content/newsblogOverlay.js
@@ -277,7 +277,7 @@ function openSubscriptionsDialog(aFolder) {
   if (subscriptionsWindow) {
     if (aFolder) {
       subscriptionsWindow.FeedSubscriptions.selectFolder(aFolder);
-      subscriptionsWindow.FeedSubscriptions.mView.treeBox.ensureRowIsVisible(
+      subscriptionsWindow.FeedSubscriptions.mView.tree.ensureRowIsVisible(
         subscriptionsWindow.FeedSubscriptions.mView.selection.currentIndex);
     }